A voter drops off their ballot in Arapahoe County. Colorado is moving toward a new 'risk-limiting' audit system, intended to ensure officials catch any equipment problems large enough to affect election results.

(Photo: Courtesy of Haley McKean, Arapahoe County clerk and recorders office)
Arapahoe County on Wednesday becomes the first in the state to test a new way of verifying election results.

It’s part of an effort to shift away from Colorado’s current system of checking election returns. That system requires staff to count 5-percent of all ballots by hand to make sure that machine tallies are accurate.

Under the new system, staff will review more ballots when election results are very close. In elections with wide margins, they’ll check fewer.

University of California-Berkeley statistician Philip Stark designed the new system, called a “risk-limiting audit.”

"Rather than saying, 'I'm going to look at some percentage of the ballots and then stop.' Risk-limiting audit says, I’m going to go collect evidence, and I’m going to keep collecting evidence until I’m convinced that the outcome is right," Stark says.

Voter advocacy groups like Common Cause are supporting the switch to risk-limiting election audits. A law passed in 2009 requires all of Colorado’s county clerks to adopt this new system by 2017.